Oscar Pistorius writes notes while sitting in the dock on the fourth day of his trial at the high court in Pretoria, South Africa, Thursday, March 6, 2014. Pistorius is charged with murder for the shooting death of his girlfriend Reeva Steenkamp on Valentine's Day in 2013. (AP Photo/Marco Longari, Pool)

PRETORIA, South Africa (AP) — As the girlfriend he shot lay dead or dying in his home, a weeping, praying Oscar Pistorius knelt at her side and struggled in vain to help her breathe by holding two fingers in her clenched mouth, a witness testified Thursday at the double-amputee runner’s murder trial.

“‘I shot her. I thought she was a burglar. I shot her,'” radiologist Johan Stipp recalled Pistorius saying in the minutes after the fatal shooting for which the celebrated athlete is on trial for murder.

A few minutes later, Stipp said, Pistorius went upstairs — the area where he had shot Reeva Steenkamp — and then returned. At that point, Stipp said he was concerned that the gun used in the shooting had not been recovered and that a distraught Pistorius was going to harm himself. The testimony did not address what Pistorius did when he went upstairs.

The testimony in a Pretoria court was the first detailed, public description of the immediate aftermath of the shooting of Steenkamp, a 29-year-old model, by the Olympian in the pre-dawn hours of Feb. 14 — Valentine’s Day — last year.

At his bail hearing last year, Pistorius said in a statement read by lawyer Barry Roux that, after he realized he had shot Steenkamp, he pulled on his prosthetic legs and tried to kick down the toilet door before finally giving up and bashing it in with a cricket bat. Inside, he said he found Steenkamp, slumped over but still alive. He said he lifted her bloodied body and carried her downstairs to seek medical help.

“It was obvious that she was mortally wounded,” Stipp said as he described what he saw at Pistorius’ villa. “At the bottom of the stairs … there was a lady lying on her back on the floor.”

As a radiologist, Stipp is a medical doctor with years of study, and he said he used his expertise to try to save the shot woman.

“I tried to assist her.” Stipp said. “I tried to open an airway.”

“She had no pulse in the neck, she had no peripheral pulse. She had no breathing movements that she made,” Stipp said.

Sitting on a courtroom bench, Pistorius bent forward and put his hand over his face, then moved them to cover both ears, as Stipp spoke. He stayed that way for a while, even when one of his lawyers reached back and touched him on the head.

“I went near her and as I bent down, I also noticed a man on the left kneeling by her side,” Stipp said under questioning by prosecutor Gerrie Nel. “He had his left hand on her right groin, and his right hand, the second and third fingers in her mouth.”

Stipp, who said he didn’t know that man was Pistorius until later, said he tried to help but Steenkamp showed no signs of life. Stipp said he noticed a wound in her right thigh, in her upper arm and in the right side of the head, and there was brain tissue around the skull.

Pistorius is charged with murder after shooting Steenkamp three times out of four shots through a toilet door in his home. Prosecutors said the athlete intentionally killed Steenkamp after an argument, but Pistorius says it was a mistake because he thought she was an intruder.

“Oscar was crying all the time,” he said. “He was praying to God, ‘Please let her live.'”

“Oscar said he would dedicate “his life and her life to God” if she would live, according to Stipp.

Pistorius, who ran at the 2012 Olympics on carbon fiber blades that brought him to be known as the Blade Runner, is charged with premeditated murder. The state has to prove its case against Pistorius completely to convict, while his defense can focus on casting doubt.

Pistorius’ lead defense lawyer, Roux, mainly avoided the gruesome details of Steenkamp’s injuries, saying he did not want to be “graphic.”

The head shot was “terrible, serious, devastating,” Roux said as he began his cross-examination of Stipp, a prosecution witness.

However, three witnesses, including Stipp, have now testified to hearing a woman screaming in Pistorius’ home, apparently boosting the case against Pistorius that there was a fight between the couple and Pistorius killed Steenkamp intentionally.

“I’m convinced that I heard a lady’s voice,” Charl Johnson, another neighbor, said earlier Thursday.

Stipp also said he believed a woman was screaming in Pistorius’ home that night, which Pistorius’ team says did not happen.

“I heard the woman screaming. I tried to ascertain … where it was coming from,” Stipp said at the start of his testimony.